Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
Title: FRANGIBLE NONLETHAL PROJECTILE
FIELD OF THE INVENTION
This invention relates to a new form of nonlethal
projectile and cartridge casing, adapted for use in
05 firearms. More particularly it relates to a frangible
projectile of preferred configuration.
BACKGROUND
In the munitions industry a variety of
projectiles have been proposed for permitting delivery of
a range of chemical agents far various purposes. These
purposes range from marking with a colouring agent, to
selective use of designer chemicals for operational
purposes such as crowd control and special operations.
There have also been various attempts to produce
a frangible projectile for toy guns and for real firearms
but none are known to have overcome satisfactorily all
the problems that may be encountered. Such problems
include:
- stable flight, for accuracy and so the
projectile will hit nose-first;
- sufficient strength to withstand the stress of
feeding and firing in a firearm yet frangible enough to
break upon impact even upon an unrigid surface;
- sufficient sealing so that a filling contained
within the projectile does not leak; and
- imperviousness to environmental extremes of
cold, heat and moisture.
THE INVENTION
The present invention is a two-piece polymer
projectile consisting of an aero dynamically shaped,
thin-shelled, frangible cap, adapted to be filled with a
flowable substance and sealed with a rear plug. It
combines the following features to overcome a number of
the problems normally associated with frangible
projectiles:
(a) the rear plug is relatively rigid in order
to contain the expansive effect of propellant gases;
(b) a recessed compartment in the rear plug
contributes to creating a forward center of gravity for
the projectile; and thereby provide a more stable flight;
(c) the barrel rifling is engaged by the
projectile in the region of the rear plug only, whereby
positive engagement with the barrel rifling imparts spin
without bursting the cap portion of the projectile;
(d) the cap itself is isolated from the rifling
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in the gun barrel by dimensioning the cap fractionally
smaller than the gun bore so as to reduce the risk of
rupture which could occur from contact with the rifling;
(e) score lines on the forward portion of the
cap provide separation of the cap release of the filling
on impact;
(f) an indentation region on the nose of the cap
facilitates flexing of the score lines for more rapid and
efficient bursting of the cap on impact;
(g) complete sealing of the filling compound
within the cap is achieved through an integral "O" ring
on the plug which mates with an encircling groove within
the cap for a snap-on sealing fit;
(h) the score lines extending down the side of
the cap do not extend over the plug.
(i) the wall thickness of the cap is selected,
in combination with material selection, to resist
breakage from lateral impact or handling, while remaining
sufficiently frangible on impact so as to be nonlethal.
Preferably the projectile is provided with an
amorphous free-flowing powder, liquid or semi-liquid
filling compound which:
(i) does not significantly change its physical
properties over a temperature range of approximately -20
degrees to plus 50 degrees Celsius; and
(ii) is of sufficient viscosity and/or adherence
to the wall of the projectile cap to prevent the
otherwise destabilizing effect of the compound spinning
at a different rate from the cap.
These and further features of the invention will
be apparent from the description of the preferred
embodiments which now follow.
SUMMARY OF THE FIGURES
Figure 1 - is a transverse sectional view of a cartridge
casing with projectile.
Figure 1a - is an end view of Figure 1.
Figure 2 - is a transverse sectional view of the plug or
base portion of the projectile.
Figure 3 - is a transverse sectional view of the cap or
casing portion of the projectile.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Figure 1 shows a projectile (1), of the type of the
invention, inserted into a cartridge casing (2). The
cartridge casing is provided with a lower energy
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propellant means, which may be in the form merely of the
standard percussion cap (3a). Alternately, a lOGJ power
gas--generating propellant (not show) may be provided.
The projectile has a forward cap portion (4) and
a plug portion or plug (5) which serves to plug the open
base region of 'the cap (4). The plug (5) is provided
with an cylindrical portion (6) and a base (7) which
serves as a plate to seal the base of the cad (4).
The base (7) is forward of the rearward end (8)
lU of the plug, providing a cavity (9) therebetween. This
cavity (9) shifts the center of mass (10) of the
projectile (1) forward of its geometric center (11),
midway between the nose (12) of the projectile (1) and
the rearward end (8) of the plug (5). This provides
stability for the projectile (1) in flight.
The plug (5) is preferably made with a wall 5a of
a thickness and of relatively ridged polymeric material
that will burst on impact. Polyethylene has been found
satisfactory. The plug (5) has a cylindrical wall (20)
which serves the function of containing the expansive
forces of expanding propellant gas, and must be
constructed accordingly.
In detail, as shown in Figure (2), the ,plug (5)
may be formed with an outer stiffening annular rim (13).
Further, it may be provided with an annular coupling
ridge (14) capable of providing '°0" ring type sealing
with the cap.
The diameter of the rim (13) may optionally be
such as to provide a tight friction fit with the inner
surface (15) of the casing (2). The diameter of this rim
may also provide a sliding fit with the inner surface of
the barrel of the firearm in which it is to be discharged
(not shown). This will permit the ring (13) to engage
the rifling on the inside of the barrel and impart
longitudinal rotation of the projectile.
The cap (4) is formed of relatively pliable,
resilient material in the form of a thin shell or casing.
The dimensions and material of the cap (4) are such as to
render it susceptible to immediate rupture on impact. A
wall thickness of .025 inches .in polyethylene has been
found satisfactory.
The cap (4) is generally cylindrical with an
aerodynamic, bullet-shaped nose (12). The base region
(16) of the cap (4) makes a tight friction fit with the
cylindrical portion (6) of the body of the plug (5).
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Preferably, the inner surface of the cap (5) is provided
with a groove (17) which is complementary to the ridge
(14) on the plug (5). Alternately the ridge (14) and
groove (17) may be reversed.
The outside diameter of the cap (4) when fitted
over the cylindrical portion (16) and ridge (14), as
assembled may, along with the entire cap (5), be of a
smaller diameter than the rim (13). This will reduce the
wear on the cap (5) due to contact with the barrel if the
rim (13) provides a tight sliding fit with the barrel.
Alternately, the cap (7), when placed over the
cylindrical portion (16), optionally by the stretched
fit, may exceed the diameter of the rim (13) sufficiently
to engage the rifling in a barrel and impart longitudinal
rotation to the projectile (1). In either case, the
barrel rifling is positively engaged by the projectile
(1) in the region of the rear plug only.
The cap (4) is provided with narrow longitudinal
strips of thinned cross-section. These "scores" or
scoring lines not cut entirely through the cap (4), but
render it easily burst upon compression by the forces of
impact. At the same time the projectile must be
sufficiently sturdy to sustain loading, and firing,
without bursting. A wall thickness at the scores (17) of
.005 inches in polyethylene has been found satisfactory.
The scores (19), numbering 6 in the preferred
embodiment, are preferably symmetrical positioned about
the axis of the cap (4), closing radially at the nose
(12j to a central region (18) of reduced wall thickness.
This central region (18) is similarly thinned as the
scored regions (19) of the cap (4). Tt covers a
relatively minor portion of the end profile of the cap
(4) at its nose end (12) and is preferably, but
optionally, slightly concave. Its purpose is to
facilitate flexing of the score lines on impact, thus
providing for more rapid and efficient busting of the cap
on impact.
The scores (19) preferably do not extend aver the
region of the "O" ring ridge (14).
The contents of the projectile may include a
powder, gas liquid, semi-liquid or other free-flowing
fluid. The use of such a filling in conjunction with
modest propellant charges, renders the projectile
nonlethal.
Thus, it will be seen from the foregoing that an
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improved nonlethal, frangible projectile is provided that
may be fired from a standard firearm.
These and further features of the invention in
its broadest and more narrow aspects are further
described and claimed in the claims which follow.
